1. Field of the Invention
The present invention relates generally to pallets and shipping trays, and more particularly to improved load bearing pallets and shipping trays comprising thermoplastic material
2. Description of Related Art
Many wooden and plastic pallets are known in the art. However, pre-existing wooden and plastic pallets are characterized by a number of disadvantages. Wooden pallets are relatively heavy and difficult to manufacture. Typical construction of such pallets utilize a first set of parallel boards forming an upper surface, and a second set of parallel boards forming a lower surface, nailed to three or more stringers positioned perpendicular to the length of the boards, and sandwiched between the upper and lower surfaces. The stringers used to separate the upper and lower deck surfaces create two openings to accommodate the arms of a forklift for lifting and moving the pallets. The wood used to construct the pallets may swell and warp if exposed to moisture. Wooden pallets are subject to rotting and splintering, and the wood may be a substrate for the growth of fungus and bacteria, especially under moist conditions. The nails used in the pallets may rust, and sometimes causes cargo damage or injuries.
Attempts to form pallets from other materials in order to avoid the disadvantages inherent in wooden pallets have been only partially successful. Prior art designs using plastics to form pallets have been characterized by a trade off between cost and weight bearing capability. Those pallets having a significant weight bearing capability tend to be heavy and expensive, whereas plastic pallets produced inexpensively typically have reduced durability and weight bearing capacity.
What is needed is a pallet design comprising a plastic material that overcomes the disadvantages of the prior art. Specifically, it is desirable to provide a pallet that is inexpensive and relatively light weight yet strong, that is formed of recyclable materials, that is stackable, that may be readily assembled on site, that may be picked up by a fork lift from all four sides, that is resistant to the growth of fungus and bacteria, and that is easily cleaned.
Accordingly, the invention is an improved load bearing pallet including at least an upper deck formed of a sheet of rigid but formable material, such as plastic or metal but preferably a thermoplastic material, with a load engaging surface on one side of the sheet and a lift engaging surface on the other. A number of features such as ridges, channels, depressions, and legs are formed in the sheet with corresponding features being defined by the sheet on the opposite side. The pallet preferably includes a peripheral channel formed around a periphery of the upper deck and nine legs positioned in three rows of three creating two gaps on each side of the pallet for the tines of a fork lift to enter to lift the pallet.
In a second embodiment, the pallet may further include at least one integral reinforcing member received within the peripheral channel. Preferably one reinforcing member is positioned within the peripheral channel on each side of the pallet, but in alternate embodiments, a unitary ring that fits around the pallet, but within the peripheral channel, may be used. The reinforcing members may be formed of any desired materials, including metal or wood. However, the reinforcing members preferably comprise a steel support structure encapsulated within a thermoplastic material. The reinforcing members are preferably bonded within the channel of the upper deck by causing the molecular structure of the thermoplastic material encapsulating the support structure to cross-link with the thermoplastic material comprising the upper deck to integrally bond the reinforcing member to the upper deck to form a unitary object.
In other embodiments, the pallet may further include a lower deck or other support structure. The lower deck is preferably formed of a single sheet of rigid but formable material, preferably a thermoplastic material, comprising a top surface and a bottom surface. A plurality of legs are formed in the top surface of the lower deck, corresponding to an equal number of legs extending from the lifting surface of the upper deck. Each leg formed in this way in the lower deck is coupled to a corresponding leg of the upper deck. The bond between the legs of the lower deck and the legs of the upper deck are preferably made by causing the molecular structure of the thermoplastic material of the upper deck to cross link to the molecular structure of the lower deck, although in alternate embodiments, other means for coupling the upper and lower decks may be used.
The lower deck may further include a plurality of channels and ridges formed in the top surface of the lower deck, which correspond to channels and ridges formed in the bottom surface. The lower deck may additionally include a plurality of reinforcing members, each preferably comprising a steel support structure encapsulated within a thermoplastic coating, although other materials may be used in alternate embodiments. The reinforcing member is received within the peripheral channel of the lower deck and is preferably bonded therein by causing the molecular structure of the thermoplastic material encapsulating the support structure to cross link with the molecular structure of the thermoplastic material of the lower deck.
The invention further includes a single deck pallet with runners. Such a pallet comprises a single sheet comprising a rigid but formable material, a load bearing surface on a first side of the sheet, and a lifting surface on an opposite second side of the sheet. A plurality of depressions are formed in the load bearing surface corresponding to an equal number of legs extending from the lifting surface. A runner is coupled to at least two of the legs. The lifting surface is substantially parallel to the load bearing surface such that features defined in the load bearing surface will have a corresponding feature defined in the lifting surface. Thus, a plurality of top channels and top ridges are formed in the load bearing surface wherein each top ridge formed in the load bearing surface corresponds to a bottom channel formed in the lifting surface and each top channel formed in the load bearing surface corresponds to a bottom ridge formed in the lifting surface.
The single sheet has four edges defining a periphery. A peripheral channel is formed adjacent to the periphery of the sheet. The rigid but formable material of the sheet comprises a thermoplastic material. The runner is coupled to one of the rows of three legs. The plurality of depressions comprises nine depressions corresponding to nine legs, the nine depressions and legs being disposed in three rows with each row having three depressions and three corresponding legs. The runner has a substantially flat upper and lower surface. The runner comprises wood or any other solid material. The runner comprises a thermoplastic covering.
At least two of the legs which are coupled to the runner each comprise a recessed portion and an exposed portion. The runner may have a flat bottom runner surface as well as a flat top runner surface. The runner is disposed in the recessed portions of the at least two of legs such that the bottom runner surface is substantially flush with the exposed portions of the at least two legs. Furthermore, the runner may be removably coupled to at least two of the legs with a locking pin or any other securing mechanism.
The invention further comprises a pallet made of two sheets, or a dual deck pallet. A first sheet, or upper deck, is coupled to a second sheet, or lower deck, to form the single pallet. The second sheet may have a structure that is substantially similar to or different from a structure of the first sheet. If the sheets are identical or substantially similar in structure, the first sheet may be nested on top of the second sheet when the pallet is disassembled and not in use. If the sheets are different in structure, the pallet may be disassembled and the first sheet may be nested on top of a first sheet of another pallet while the second sheet may be nested on top of a second sheet of the other pallet.
The first sheet comprises a first rigid but formable material. The first sheet has a first structure including a first external surface, a first internal surface substantially parallel and opposite to the first external surface, and a first plurality of channels and ridges. The first plurality of channels and ridges formed in the first sheet result in a plurality of channels and ridges in the first external surface and a corresponding plurality of ridges and channels in the first internal surface. Since the first internal surface is substantially parallel to the first external surface, each ridge formed in the first external surface corresponds to a channel formed in the first internal surface, and each channel formed in the first external surface corresponds to a ridge formed in the first internal surface.
The second sheet comprises a second rigid but formable material, which may be similar to or different from the first rigid but formable material. The second sheet has a second structure which may be different from or substantially similar to the first structure. The second structure includes a second external surface, a second internal surface substantially parallel and opposite to the second external surface, and a second plurality of outer channels and outer ridges. The second plurality of channels and ridges formed in the second sheet result in a plurality of channels and ridges in the second external surface and a corresponding plurality of ridges and channels in the second internal surface. Since the second internal surface is substantially parallel to the second external surface, each ridge formed in the second external surface corresponds to a channel formed in the second internal surface and each channel formed in the second external surface corresponds to a ridge formed in the second internal surface formed in the second external surface wherein each ridge in the second external surface corresponds to a channel formed in the second internal surface and each channel formed in the second external surface corresponds to a ridge formed in the second internal surface.
The first and second rigid but formable material comprises a thermoplastic material. The first and second sheet each comprise a peripheral channel formed adjacent to a periphery of each sheet.
The pallet may include a first reinforcing member received within the peripheral channel of the first sheet. The first reinforcing member comprises a structural member encapsulated within a thermoplastic material. In addition, the pallet may also include a second reinforcing member received within the peripheral channel of the second sheet. The second reinforcing member comprises a structural member encapsulated within a thermoplastic material. Furthermore, each sheet may include additional reinforcing members. When the second sheet is different in structure from the first sheet, the first reinforcing member has an oval profile with a first height while the second reinforcing member has a square profile with a second height that is less than the first height.
In the dual deck pallet, the first internal surface and the second internal surface face each other. Accordingly, the first external surface and the second external surface face outwardly away from each other. The pallet further comprises a plurality of columns disposed between and coupled to the first sheet and the second sheet. The columns each comprise a bottom portion, a top portion, and a tube extending from the bottom portion to the top portion. The pallet further comprises a plurality of clamping pins, wherein a clamping pin is disposed in the tube of each of the at least four columns.
The first sheet has a first plurality of apertures. The second sheet has a second plurality of apertures. Each clamping pin extends through an aperture of the first sheet and an aperture of the second sheet. Each clamping pin has a hollow core. Each clamping pin comprises a first lip at a first end and a second lip at a second end, wherein the first lip has a first diameter greater than a diameter of the apertures of the first sheet, and wherein the second lip has a second diameter greater than a diameter of the apertures of the second sheet. The first sheet may comprise a first plurality of shoulders, wherein a shoulder surrounds each aperture. The second sheet comprises a second plurality of shoulders, wherein a shoulder surrounds each aperture. The lip at the first end of each clamping pin rests against the shoulder surrounding a corresponding aperture of the first sheet. The lip at the second end of each clamping pin rests against the shoulder surrounding a corresponding aperture of the second sheet. A rigid washer is disposed between the lips of the clamping pin and the shoulder of the corresponding aperture on the sheet. The washer serves to spread the compressional load from the lips of the clamping pin onto a wider area of the sheet to provide a stronger connection.
The dual deck pallet further comprises a plurality of rigid inserts, wherein a rigid insert is disposed in a top portion and a bottom portion of the hollow core of each clamping pin. Each rigid insert comprises a recess. The dual deck pallet further comprises a plurality of anti-skid plugs, wherein a plug is disposed in each recess of each rigid insert.
In one aspect, the second sheet may have a structure different from a structure of the first sheet. The second sheet, or lower deck, may include less material in its composition. Thus, the second sheet may include a plurality of large, central openings, or gaps. The second sheet may also have a height less than a height of the first sheet. In such an embodiment, the second sheet may include a reinforcing member with a square profile while the first sheet may include a reinforcing member with an oval profile. The pallet may be disassembled to allow for nesting of the sheets. In this embodiment where the structure of the second sheet differs from that of the first sheet, the first sheet may nest upon a first sheet of another pallet while the second sheet may nest upon a second sheet of the other pallet.
In another aspect, the second sheet may have a structure substantially similar to the structure of the first sheet. In this embodiment, the pallet may be disassembled and the first sheet may nest on top of the second sheet since both structures are identical or substantially similar.
The invention further comprises a method for stacking decks when the decks are not bearing a load. The method comprises: providing a first deck having a first top surface and a first bottom surface substantially parallel and opposite to the first top surface; forming a first plurality of channels and ridges in the first deck to form a plurality of channels and ridges in the first top surface and a corresponding plurality of channels and ridges in the first bottom surface wherein each ridge in the first top surface corresponds to a channel in the first bottom surface and each channel in the first top surface corresponds to a ridge in the first bottom surface; providing a second deck with a substantially similar structure as a structure of the first deck, wherein the second deck has a second top surface and a second bottom surface substantially parallel and opposite to the second top surface; forming a second plurality of channels and ridges in the second deck to form a plurality of channels and ridges in the second top surface and a corresponding plurality of channels and ridges in the second bottom surface wherein each ridge in the second top surface corresponds to a channel in the second bottom surface and each channel in the second top surface corresponds to a ridge in the second bottom surface; and stacking the first deck on top of the second deck wherein a ridge in the first bottom surface nests on top of a channel in the second top surface and a channel in the first bottom surface nests on top of a ridge in the second top surface.
It is to be expressly understood that the terms xe2x80x9cfirst deckxe2x80x9d and xe2x80x9csecond deckxe2x80x9d include decks which are coupled to each other to form a dual deck pallet, as well as decks which are separate from each other wherein each deck is a pallet unto itself.
The method further comprises forming a first plurality of depressions in the first top surface corresponding to an equal number of legs extending from the first bottom surface; and forming a second plurality of depressions in the second top surface corresponding to an equal number of legs extending from the second bottom surface. The method may further comprise nesting each leg extending from the first bottom surface of the first deck with a corresponding depression on the second top surface of the second deck.
If a first runner is removably coupled to at least two of the legs extending from the first bottom surface and a second runner is removably coupled to at least two of the legs extending from the second bottom surface when the decks are in use, the method further comprises: removing the first runner from the at least two legs extending from the first bottom surface; removing the second runner from the at least two legs extending from the second bottom surface; and nesting each leg extending from the first bottom surface with a corresponding depression on the second top surface.